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Question for Vern or SFDon about M30 break-in

Hi. I posted a question on the E28 board about the M30 engine and was told you were the guys to ask. I've just overhauled my '85 535i. I pulled the motor and did rings, bearings, valves, honed cylinders and cam. Everything was in good shape so kept old pistons. Did the first start up yesterday - started beautifully and ran well. So far have just let it idle for about 15 minutes, shut it off and did the final torque of the head while warm and drained the oil. I plan to do the first road test in a few days. I've read a lot of articles about engine break-in procedure and know about varying RPM, not lugging it, etc. I probably will tend to treat it on the gentle side - not a red-line shifter even when the engine is broken in. There is some thought that the break-in should be pretty aggressive and the revs taken up gradually and occasionally or else the rings won't seat properly. What are your opinions on this? Have I done the wrong thing already by letting it idle too much? Do you know how they break in the cars at the factory?
Thanks.
Rick Z

Engine Break in

The generally accepted rule for M30 (and most other BMW engines from the 80's) is 1500 miles, no hard acceleration, no long periods at same rpm, drain the oil at 1500 to look for metal shavings or other pieces and parts. Also, recheck your valve clearances at 1500.

I have also heard the theory that you should gradually increase the load you put on the engine over the 1500 mile break in period, that by increasing the load you are getting proper engine temp and thus properly expanding the piston rings against the piston walls. The theory is that without running the engine up in the rpms, you are not creating a high enough pressure in the cylinders top push the piston rings against the cylinder walls, and as a result you will not properly wear down the honing peaks on the cylinder walls. The end result would be oxidizing of oil on the cylinder walls which creates glazing and a couple common side effects of cylinder glazing are lower cylinder pressures and oil leakage around the piston rings.

But that's just hearsay, which is only a couple letters removed from heresy

From the Owners manual...

The first 1,200 miles, do not exceed 2/3 of the road speed in each gear.

Or: 20 mph in 1st, 40 mph in second, 60 mph in 3rd, and about 90 mph top speed during break in. Do not use wide open throttle during break in, nor if an auto tranny, do not use the throttle kick down to shift.

Do not run more the 4,000 rpms, in other words.

Do a first oil change at 600 miles and a second oil change at 1,200 miles. Don't forget, if you have an oil cooler to run to full running temp to flush out the oil cooler circuit.

When I had an E28 535i, I ran all the way to redline with an engine I took to over 303,000 miles before junking (though not from new). These cars are made to run at max performance for a few hours at a time.
SoCalVern
86 Sonderlakierung 745i
88 Jag VDP (Neglected stepchild)